Facility and method for refrigerating a fluid

ABSTRACT

Certain embodiments of the invention relate to a facility for refrigerating a fluid to a cryogenic temperature, comprising a circuit for the fluid to be refrigerated, comprising an upstream end connected to a source and a downstream end connected to a refrigerated and/or liquefied fluid collection member, the facility comprising at least one exchanger for precooling the fluid leaving the upstream end, the precooling exchanger exchanging heat with a precooling circuit composed of a flow of vaporization gas from a user, the facility further comprising a heat exchanger assembly for cooling by heat exchange with the circuit of fluid to be cooled downstream of the precooling exchanger, the facility comprising a device for cooling by heat exchange with at least a part of the cooling heat exchanger assembly, said cooling device comprising a first refrigerator with a refrigeration cycle of a cycle gas in a working circuit, the cycle gas preferably comprising hydrogen and/or helium, the working circuit of the first refrigerator comprising a member for compressing the cycle gas, a member for cooling the cycle gas, a member for expanding the cycle gas and a member for heating the cycle gas, the precooling exchanger being composed of at least one of the following materials: stainless steel or grades of stainless steel, Inconel, nickel, titanium or plastic material compatible with use at cryogenic temperatures.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a § 371 of International PCT Application PCT/EP2021/067619, filed Jun. 28, 2021, which claims the benefit of FR2008057, filed Jul. 30, 2020, both of which are herein incorporated by reference in their entireties.

FIELD OF THE INVENTION

The invention relates to a plant and to a process for the refrigeration of a fluid.

BACKGROUND OF THE INVENTION

Gas liquefaction facilities are designed to deliver the liquefied gas at saturation (Tout=Tsat (Pout)). Thus, a certain amount of gas results from the vaporization of the liquid (boil-off) to be generated. In order to limit this, the gas produced can be subcooled during its production by the liquefier. This does not regulate or partially regulates the management of a return of vaporization gas (for example generated in the empty tanks during the filling of them, typically mobile tanks, and the like).

The thermal integration of cold gas resulting from depressurizations, so-called “piston” effects or other liquid vaporization, preferentially of liquid hydrogen, is complex to integrate in a plant for production of liquefied gas.

The recovery of cold energy from these vaporization gases is known, cf. for example US2009158774A.

The solutions are not satisfactory because these returns of vaporization gas fluctuate over time and in return thermodynamic conditions (temperature/pressure/molar amount which are variable, and the like).

For this reason, the known facilities are not suitable for these fluctuations as a result of the heat gradients.

One known solution consists in returning this vaporization gas via a member for distribution at different thermal levels in the plant. The production of the plant can, however, be disrupted because of these variable returns as a result of the incorrect measurement of temperature or of the trapping of impurities locally in the exchange blocks, it being possible for these contaminants to be swept along by these return gases.

Another solution consists in providing local recondensation of this vaporization gas. However, this requires an additional source of cold or requires oversizing the production unit for its erratic requirements, creating potential instabilities and significant excess costs.

One aim of certain embodiments of the present invention is to overcome all or some of the abovementioned disadvantages of the prior art.

SUMMARY OF THE INVENTION

In certain embodiments, the invention more particularly relates to a plant for refrigeration of a fluid down to a cryogenic temperature, and in particular for the liquefaction of hydrogen, comprising a circuit of fluid to be cooled, comprising an upstream end connected to a source and a downstream end connected to a member for collecting the cooled and/or liquefied fluid, the plant comprising at least one exchanger for precooling the fluid exiting from the upstream end, said precooling exchanger being in heat exchange with a precooling circuit composed of a stream of vaporization gas of a user, the plant additionally comprising a set of heat exchanger(s) for cooling in heat exchange with the circuit of fluid to be cooled downstream of the precooling exchanger, the plant comprising at least one device for cooling in heat exchange with at least a part of the set of cooling heat exchanger(s), said cooling device comprising a first refrigerator having a cycle of refrigeration of a cycle gas in a working circuit, the cycle gas preferably comprising hydrogen and/or helium, the working circuit of the first refrigerator comprising a member for compression of the cycle gas, a member for cooling the cycle gas, a member for expanding the cycle gas and a member for reheating the cycle gas.

In an effort to overcome the deficiencies of the prior art discussed supra, the plant according to the invention, furthermore in accordance with the generic definition which the above preamble gives thereof, the precooling exchanger can include one of at least of the following materials: stainless steel or grades of stainless steel, Inconel, nickel, titanium or plastic compatible with use at cryogenic temperatures.

Furthermore, embodiments of the invention can comprise one or more of the following characteristics:

-   -   the precooling exchanger is of the plate, tube or shell and tube         type,     -   the precooling exchanger is also in heat exchange with a circuit         of refrigerant, for example liquefied nitrogen.

The invention also relates to a process for the refrigeration of a fluid down to a cryogenic temperature using a refrigeration device in accordance with any one of the characteristics above or below, in which the fluid to be cooled is circulated in the circuit of fluid to be cooled and, prior to it being cooled by a first refrigerator in the set of cooling heat exchanger(s), the fluid is precooled in the precooling exchanger by heat exchange with a stream of vaporization gas of the precooling circuit.

According to other possible distinctive features:

-   -   the stream of vaporization gas of the precooling circuit is         circulated intermittently in the precooling circuit, that is to         say that the precooling exchanger is not continually cooled by         the stream of vaporization gas,     -   the precooling exchanger endures mean temperature differences of         between 50 and 100 K between, on the one hand, the situation         where a stream of vaporization gas is circulated in the         precooling circuit and, on the other hand, the situation where a         stream of vaporization gas is not circulated in the precooling         circuit,     -   the precooling exchanger is also in heat exchange with a circuit         of refrigerant, for example liquefied nitrogen, the refrigerant         being circulated in said circuit in order to cool the precooling         exchanger when the precooling exchanger is not cooled by the         stream of vaporization gas to a predetermined cooling level.

The invention can also relate to any alternative device or method comprising any combination of the characteristics above or below within the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

Other distinctive features and advantages will become apparent on reading the description below, made with reference to the figures, in which:

FIG. 1 represents a diagrammatic and partial view illustrating an example of structure and of operation of an exemplary embodiment of a refrigeration plant according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The refrigeration plant 1 illustrated is designed, for example, for the liquefaction of a gas, for example hydrogen.

The plant 1 comprises a circuit 2 of fluid to be cooled comprising an upstream end connected to a gas source 21. The source 21 comprises, for example, a hydrogen network, an electrolyser, a steam methane reforming (SMR) system or any other source of production of gas (hydrogen in particular) which will be liquefied or cooled to a temperature close to its normal liquefaction temperature at the heart of the plant 1.

The circuit 2 comprises a downstream end connected to a member 22 for collecting the cooled and/or liquefied fluid, for example a liquefied gas storage vessel.

The plant 1 comprises an exchanger 3 for precooling the fluid exiting from the upstream end 21. This precooling exchanger 3 carries out a heat exchange with a precooling circuit 9 in which a stream of vaporization gas of a user 10 can circulate. For example, the vaporization gas is hydrogen which originates from a tank 10 to be filled, from a stationary or mobile storage vessel or any other part of the plant or from an element external to the plant 1.

The plant 1 additionally comprises a set of heat exchanger(s) 4, 5 for cooling in heat exchange with the circuit 2 of fluid to be cooled positioned in series downstream of the precooling exchanger 3. The separate exchangers 4, 5 illustrated can be joined for any useful purpose to give a single exchanger.

The plant 1 comprises a device 6, 11 for cooling in heat exchange with at least a part of the set of cooling heat exchanger(s) 4, 5.

The cooling device comprises a first refrigerator 6 having a cycle of cooling a cycle gas in a working circuit, the cycle gas preferably comprising hydrogen and/or helium. The working circuit of the first refrigerator 6 comprises a member 7 for compression of the cycle gas (for example, one or more compressors), a member 5 for cooling the cycle gas (for example, one or more heat exchangers), a member 8 for expansion of the cycle gas (for example, one or more turbines and/or valves) and a member 5 for reheating the cycle gas (for example, one or more heat exchangers).

The precooling exchanger 3 is composed of one at least of the following materials: stainless steel or grades of stainless steel, Inconel, nickel, titanium or plastic compatible with use at cryogenic temperatures (for example of less than minus 150° C.). Thus, the returns of cold vaporized gas of the plant 1 are carried out within at least one precooling exchanger 3 preferentially made of stainless steel or any other material exhibiting outstanding mechanical characteristics making it possible to endure heat gradients much greater than those normally managed in the known facilities.

This architecture makes it possible to withstand blasts of cold which are variable in amount and in time.

In the case of hydrogen, the material will be compatible with operating temperatures of less than −196° C.

This thus makes it possible to take advantage of the cold energy available from the returns of cold gas in precooling the flow of gas to be cooled. When there is no return of cold gas, the precooling exchanger 3 can remain in the cold condition by virtue of thermal insulation, if need be, and, when a flow of vaporization gas arrives, its cold energy can be recovered. If no cold return is available or is not available at the expected design flow level, the need for precooling can be temporarily satisfied by the use of liquid nitrogen or of another cooling gas or liquid available on site. The exchanger 3 should in this case be sized with three passages and preferably benefit from an existing utility.

The great difference in temperature within the exchanger 3 makes it possible to have a very compact exchange block (logarithmic mean differences in temperature of 50 to 100 K, for example). In the light of the ratios of the hot gas to be cooled to the cold vaporization gases, it is possible to carry out a precooling down to a level of approximately −40° C. via a simple precooling heat exchanger 3. This requires neither a contribution of electrical power nor complex specific control and with very low installation costs.

In the example represented, a single precooling heat exchanger is provided. Of course, several precooling exchangers 3 can be provided. For example, two separate precooling heat exchangers 3 can be provided. A first precooling heat exchanger 3 receives, for example, a vaporization gas (for example, return from a liquefied gas tank truck) at a temperature typically of the order of 30 K up to 80 K or 100 K, for example, in order to precool the hydrogen stream in the cycle, and a second precooling heat exchanger 3 further upstream in order to precool the gas stream to be cooled originating from the source 21 by virtue of the remaining cold energy (for example, between 80 K and 300 K).

The fact of reheating the return vaporization gas flow, if it is contaminated by any impurity, makes it possible to be freed from a conventional operating problem related to the recondensation technology (in this specific case, there is a risk of solidification of the impurities and of storing them in the cold exchangers of the process, as far as potentially a blockage or, in some cases, the generation of an explosive atmosphere).

As illustrated in dotted lines, the precooling heat exchanger 3 can, if appropriate, also be in heat exchange with a circuit 12 of refrigerant, for example liquefied nitrogen (or any other cold source). This refrigerant circuit 12 makes it possible, if appropriate, to keep the precooling exchanger 3 cold when the vaporization gas flow is insufficient or zero. Thus, this refrigerant circuit 12 can be used alone to cool the precooling heat exchanger 3 or in addition to the circuit 9 through which the vaporization gas stream can pass in transit.

As also illustrated, the cooling device can comprise another member 11 for cooling in heat exchange with a part of the set of heat exchanger(s) 4, in particular between the precooling exchanger and the cooling carried out by the first refrigerator 6. This additional cooling member 11 can be a second refrigerator providing intermediate cooling between the precooling exchanger 3 and the first refrigerator 6.

This second refrigerator 11 can use, for example, another fluid, for example nitrogen. For example, this second refrigerator 11 makes it possible to precool the fluid to a temperature of between 70 and 100 K. After this cooling, the first refrigerator 6 provides additional cooling of the circuit 2 down to the target temperature (temperature of liquefaction of the hydrogen, for example).

The structure and the process make it possible to easily recover, without constraint and in a relatively inexpensive fashion, vaporization gas cold energy generated intermittently.

The solution advantageously applies to the liquefaction of hydrogen but can also apply to the liquefaction of helium, methane, nitrogen, oxygen or any other fluid.

The precooling exchanger 3 is configured in order to withstand variations in temperature of greater than 200 K or 150 K, for example.

This exchanger 3 can be provided in order to precool hydrogen, initially at ambient temperature, via an exchange of heat with a stream at cryogenic temperature, in particular of less than or equal to 80 K.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.

“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited. 

1-7. (canceled)
 8. A plant for refrigeration of a fluid to a cryogenic temperature, for the liquefaction of hydrogen, the plant comprising: a circuit of fluid to be cooled, comprising an upstream end connected to a source and a downstream end connected to a member configured to collect the cooled and/or liquefied fluid; a single exchanger configured to precool the fluid exiting from the upstream end, said precooling exchanger being in heat exchange with a precooling circuit composed of a stream of vaporization gas of a user; a set of heat exchanger(s) configured to cool in heat exchange with the circuit of fluid to be cooled downstream of the precooling exchanger; a cooling device configured to cool in heat exchange with at least a part of the set of cooling heat exchanger(s), said cooling device comprising a first refrigerator having a cycle of refrigeration of a cycle gas in a working circuit, the cycle gas comprising hydrogen and/or helium, the working circuit of the first refrigerator comprising a member configured to compress the cycle gas, a member configured to cool the cycle gas, a member configured to expand the cycle gas and a member configured to reheat the cycle gas, wherein the precooling exchanger comprises at least one of the following materials: stainless steel or grades of stainless steel, Inconel, nickel, titanium, and plastic compatible with use at cryogenic temperatures.
 9. The plant as claimed in claim 8, wherein the precooling exchanger is of the plate, tube or shell and tube type.
 10. The plant as claimed in claim 8, wherein the precooling exchanger is also in heat exchange with a circuit of refrigerant, for example liquefied nitrogen.
 11. A process for the refrigeration of a fluid down to a cryogenic temperature using a refrigeration device in accordance with claim 8, the process comprising the steps of: circulating the fluid to be cooled in the circuit of fluid to be cooled; and, prior to cooling the fluid by a first refrigerator in the set of cooling heat exchanger(s), precooling the fluid in the precooling exchanger by heat exchange with a stream of vaporization gas of the precooling circuit.
 12. The process as claimed in claim 11, wherein the stream of vaporization gas of the precooling circuit is circulated intermittently in the precooling circuit, that is to say that the precooling exchanger is not continually cooled by the stream of vaporization gas.
 13. The process as claimed in claim 11, wherein the precooling exchanger endures mean temperature differences of between 50 and 100 K between, on the one hand, the situation where a stream of vaporization gas is circulated in the precooling circuit and, on the other hand, the situation where a stream of vaporization gas is not circulated in the precooling circuit.
 14. The process as claimed in claim 12, wherein the precooling exchanger is also in heat exchange with a circuit of refrigerant, for example liquefied nitrogen, the refrigerant being circulated in said circuit in order to cool the precooling exchanger when the precooling exchanger is not cooled by the stream of vaporization gas to a predetermined cooling level. 